Load-adaptive smooth startup method for sensorless field-oriented control of permanent magnet synchronous motors

ABSTRACT

A field oriented control (FOC) system and method provides smooth field-oriented startup for three-phase sensorless permanent magnet synchronous motors (PMSMs) despite the absence of load information. The system uses the rotor flux projection on the d- or q-axis to determine whether the stator flux current reference being applied during reference startup phase is sufficient to spin the PMSM, thereby providing smooth operation during the reference startup phase and saving energy relative to applying rated current. The system also determines a suitable initial value for the stator torque current reference to use at the start of closed-loop sensorless FOC control mode based on an angle difference between the reference and estimated angles. Since this angle difference is reflective of the load on the PMSM, the selected initial value allows the system to achieve a smooth transition from reference startup mode to closed-loop sensorless FOC control mode.

TECHNICAL FIELD

This disclosure generally relates to sensorless control of permanentmagnet synchronous motors (PMSMs), and specifically to load-adaptivesmooth startup techniques.

BACKGROUND

Permanent magnet synchronous motors (PMSMs) are used in a wide varietyof applications. FIG. 1 is a simplified diagram of an example PMSM 100.PMSMs typically comprise a rotor 108 configured to rotate within astator 102. Permanent magnets 106 are mounted on or buried within therotor 108 (PMSMs with permanent magnets that are buried within the rotorare referred to as interior permanent magnet, or IPM, motors). Thestator 102 includes a number of electrical windings 104 arranged tosurround the rotor 108. During operation, electrical current through thewindings 104 sets up a magnetic field within the air gap 110 between therotor 108 and the stator 102, and the interaction between the magnets106 and the magnetic field causes the rotor 108 to rotate, producingtorque. The speed and direction of the rotor 108 can be controlled bycontrolling the current through the stator windings 104.

PMSMs are often controlled using field oriented control (FOC)techniques. However, since sensorless PMSMs lack directly measured loadinformation, smooth transition from the stopped state to closed-loopsensorless FOC control of a PMSM can be difficult. This is because,lacking information regarding the load on the PMSM, the FOC controlsystem may be designed to apply an excessive amount of torque during thetransition to ensure that the motor achieves a minimum amount of speedto generate usable back-electromagnetic force (back-EMF) information.This excessive torque can cause the motor to over-speed or stall.

The above-described is merely intended to provide an overview of some ofthe challenges facing conventional motion control systems. Otherchallenges with conventional systems and contrasting benefits of thevarious non-limiting embodiments described herein may become furtherapparent upon review of the following description.

SUMMARY

The following presents a simplified summary of one or more embodimentsin order to provide a basic understanding of such embodiments. Thissummary is not an extensive overview of all contemplated embodiments,and is intended to neither identify key or critical elements of allembodiments nor delineate the scope of any or all embodiments. Itspurpose is to present some concepts of one or more embodiments in asimplified form as a prelude to the more detailed description that ispresented later.

One or more embodiments of the present disclosure provide systems andmethods for achieving smooth field-oriented startup for three-phasesensorless PMSMs with unknown load. Beginning with the PMSM at rest, areference startup FOC phase begins when a motor control system graduallyincreases a current reference used to drive the motor. As the currentreference is increased, the motor control system determines the rotorflux projection on the reference d- or q-axis, and uses this projectionto determine whether the current reference being applied during thereference startup phase is sufficient to spin the PMSM. The system cancontinue increasing the current reference until the rotor fluxprojection reaches a defined level, which causes the motor to spin withrespect to the reference speed.

For the transition from the reference startup FOC phase to theclosed-loop sensorless FOC control phase, the motor control systemdetermines the offset between the reference angle and the estimatedangle, which is a function of the load on the PMSM. The control systemthen determines an initial reference value for the applied current basedon this angle difference, and uses this initial reference value as thestarting point for the closed-loop sensorless FOC phase, graduallytransitioning the current reference signals to the initial values of theclosed-loop sensorless FOC phase. Since this initial reference value isbased on the load seen by the PMSM, the transition from the referencestartup FOC phase to the closed-loop sensorless FOC control phase willbe smooth.

For transition back to reference startup control from the closed-loopsensorless FOC control, the current reference previously obtained duringreference startup control can be used as an initial value.

The following description and the annexed drawings set forth hereindetail certain illustrative aspects of the one or more embodiments.These aspects are indicative, however, of but a few of the various waysin which the principles of various embodiments can be employed, and thedescribed embodiments are intended to include all such aspects and theirequivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram of an example PMSM.

FIG. 2 is a simplified diagram of an example control system for asensorless PMSM.

FIG. 3 illustrates transition of a PMSM control system from referencestartup FOC control mode to closed-loop sensorless FOC control mode.

FIG. 4 is a block diagram of an example PMSM control system.

FIG. 5 is a block diagram of an example configuration for a PMSM controlsystem that implements one or more features for smooth transitioningbetween reference startup FOC control and closed-loop sensorless FOCcontrol.

FIG. 6 is a set of timing charts illustrating the values of speedreference ω_(Ref), projection λ_(r,sd), angle reference Δθ, stator fluxcurrent reference I_(sdRef), and stator torque current referenceI_(sqRef) over time for an example control sequence of a PMSM.

FIG. 7 is a graph illustrating projection of rotor flux λ_(r) on thereference q,d coordinate system.

FIG. 8 is a graph of the projection of current reference I_(sdRef) onthe estimated d,q coordinate system, showing the angle difference Δθbetween the I_(sdRef) vector and the estimated rotary coordinate frame.

FIG. 9 is a block diagram of an example configuration for a PMSM controlsystem running in closed-loop sensorless FOC control mode.

FIG. 10 is a set of timing charts illustrating transition fromclosed-loop sensorless FOC control back to reference startup control.

FIG. 11A is a flowchart of a first part of an example methodology forsmoothly transitioning from reference startup FOC control of a PMSM toclosed-loop sensorless FOC control.

FIG. 11B is a flowchart of a second part of an example methodology forsmoothly transitioning from reference startup FOC control of a PMSM toclosed-loop sensorless FOC control.

FIG. 12 is a block diagram representing an exemplary networked ordistributed computing environment for implementing one or moreembodiments described herein.

FIG. 13 is a block diagram representing an exemplary computing system oroperating environment for implementing one or more embodiments describedherein.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings,wherein like reference numerals refer to like elements throughout. Inthe following description, for the purposes of explanation, numerousspecific details are set forth in order to provide an understanding ofthis disclosure. It is to be understood, however, that such embodimentsmay be practiced without these specific details, or with other methods,components, materials, etc. In other instances, structures and devicesare shown in block diagram form to facilitate describing one or moreembodiments.

Permanent magnet synchronous motors (PMSMs) are used in a wide varietyof applications. For example, many industrial automation applicationsrely on PMSMs and their associated control systems to drive motion ofsystem components (e.g., machining or material handling robots,conveyors, tooling machines, hand tools, etc.). PMSMs are also used inthe traction and/or propulsion systems of some electric vehicle designs,including but not limited to electric or hybrid electric automobiles,bicycles, forklifts and other industrial vehicles, scooters, railwayvehicle such as trains, and other such vehicles. PMSMs also haveapplication in building infrastructure and HVAC (heating, ventilating,and air conditioning) applications that require speed or motion control,such as fans and pumps. PMSMs can also be found in many home andindustrial appliances; for example, PMSMs can be used drive the drums ofhome or industrial washing machines, to control the spinning ofcentrifuges, or to control the motion of other such appliances.

FIG. 2 is a simplified diagram of an example control system for asensorless PMSM. PMSMs are often controlled using field oriented control(FOC) methods. Control system 206 drives the PMSM 204 in accordance witha speed reference signal. A 3-phase inverter 202 controls the 3-phase ACpower to the PMSM's stator windings based on control signals (e.g.,pulse width modulation signals, space vector modulation signals, etc.)generated by the control system 206. The control system 206 estimatesthe angle and speed of the PMSM based on measured stator currents (inthe example illustrated in FIG. 2, only two phases are measured, sincethe third phase can be calculated by the control system based onmeasurements of the other two phases).

PMSMs are often controlled using field oriented control (FOC)techniques. According to FOC, the flux and torque components of thestator currents are controlled independently by the control system basedon the external speed reference signal and the estimated rotor position.For sensorless motors, the control system estimates the rotor positionbased on the back electromagnetic force (back-EMF) measured from themotor windings. However, before closed-loop control can be achieved, thePMSM must first be rotating at a minimum speed in order for a sufficientamount of back-EMF to be generated for the control system to accuratelyestimate the rotor angle. Consequently, FOC control systems forsensorless PMSMs typically execute a two-stage startup procedure,illustrated in FIG. 3.

From the stopped position, the control system first executes a referencestartup FOC control phase, in which the control system performsopen-loop control of the motor using internally generated referencesignals in order to transition the motor from zero speed to the minimumspeed required for closed-loop control. During this phase, the speedloop is open, and estimated angle and speed are not used. The controlsystem typically uses a reference angle together with an applied currentreference in order to attract the poles of the rotor's permanent magnetsand initiate motion. In accordance with FOC control techniques, thereference angle is used to rotate the d-axis and q-axis of the d-qcoordinate system in order to spin the motor from zero speed to theminimum speed. The control system may use any suitable acceleration togenerate current reference signals (e.g., a ramping or steppingfunction) until the minimum speed is reached. When the minimum speed foraccurate rotor position estimation is achieved, the control systemswitches to closed-loop sensorless FOC control, which performs closedloop control of the PMSM based on an external speed reference signal andthe estimated position and speed determined based on the measuredback-EMF. Closed-loop sensorless FOC control uses the estimated angle torotate the d-axis and q-axis in order to apply torque and flux controlin accordance with the speed control reference signal.

The startup procedure for a sensorless PMSM can be difficult given theabsence of load information, since the amount of current required toinitiate spinning of the motor is a function of the load on the motor.During startup, it is common to apply the rated current for the motor asa default in order to initiate spinning of the motor. However, since therated current is typically greater than the current required to spin themotor, application of the rated current needlessly wastes energy.Moreover, the excessive current applied during the reference startupphase can make smooth transition from the reference startup phase to theclosed-loop sensorless FOC control phase difficult.

A common approach for transitioning from the reference startup phase tothe closed-loop sensorless FOC control phase is to gradually transitionfrom the reference angle used to drive the motor during the referencestartup phase to the estimated angle used during the closed-loopsensorless FOC control phase. However, in the absence of loadinformation, it can be difficult to determine the appropriate amount oftorque to apply as the starting point for the closed-loop control phase.As a result, inappropriate torque during the angle transition introducesa speed error, which can cause the motor to stall or over-speed if largeenough. For some types of electric motor applications, such as electricvehicles, these speed errors are not acceptable.

Systems and methods described herein relate to techniques for achievingsmooth and energy-efficient startup FOC control and transition betweenreference startup FOC control and closed-loop sensorless FOC control.According to one or more embodiments, the rotor flux projection on thed- or q-axis is used to adjust the current reference generated by themotor control system in order to spin the motor smoothly during thereference startup FOC phase without the need for load information.

In addition, once the system determines that a sufficient amount ofcurrent reference is being applied to spin the PMSM, the systemdetermines the difference between the reference angle and the estimatedangle, which is assumed to be a function of the load on the PMSM. Thesystem uses this angle difference to determine an initial torquereference for the closed-loop sensorless FOC control phase. This initialtorque reference can facilitate smooth transition from reference startupFOC control to closed-loop sensorless FOC control.

FIG. 4 is a block diagram of an example PMSM control system according toone or more embodiments. PMSM control system 402 can include a speedcontrol component 404, a startup current reference component 406, astartup angle reference component 408, a field weakening component 410,an estimation component 412, an Iq control component 414, an Id controlcomponent 416, a transformation component 418, one or more processors420, and memory 422. In various embodiments, one or more of the speedcontrol component 404, startup current reference component 406, startupangle reference component 408, field weakening component 410, estimationcomponent 412, Iq control component 414, Id control component 416,transformation component 418, the one or more processors 420, and memory422 can be electrically and/or communicatively coupled to one another toperform one or more of the functions of the PMSM control system 402. Insome embodiments, components 404, 406, 408, 410, 412, 414, 416, and 418can comprise software instructions stored on memory 422 and executed byprocessor(s) 420. The PMSM control system 402 may also interact withother hardware and/or software components not depicted in FIG. 4. Forexample, processor(s) 420 may interact with one or more external userinterface devices, such as a keyboard, a mouse, a display monitor, atouchscreen, or other such interface devices.

Speed control component 404 can be configured to control the value of atorque reference I_(sqRef) based on the error between a speed referenceω_(Ref) and an estimated speed ω_(Est) during closed-loop sensorless FOCcontrol mode. Startup current reference component 406 can be configuredto control values of a flux reference I_(sdRef) and torque I_(sqRef)during reference startup control mode. Startup angle reference component408 can be configured to determine a value of a reference angle θ_(Ref)during reference startup control mode. Field weakening component 410 canbe configured to control the value of flux reference I_(sdRef) duringclosed-loop sensorless FOC control mode. Estimation component 412 can beconfigured to determine estimated values for the motor's position andvelocity based on back-EMF values measured from the motor windings.

Iq control component 414 can be configured to control a torque referencevoltage value V_(sq) based on a detected error between a measured statorcurrent value I_(sq) and its corresponding reference value I_(sqRef). Idcontrol component 416 can be configured to control a flux referencevoltage value V_(sd) based on a detected error between a measured statorcurrent value I_(sd) and its corresponding reference value I_(sdRef).Transformation component 418 can be configured to perform mathematicaltransformations on signals generated or measured by the PMSM controlsystem 402 (e.g., forward and reverse Park transforms, Clarketransforms, etc.).

The one or more processors 420 can perform one or more of the functionsdescribed herein with reference to the systems and/or methods.disclosed. Memory 422 can be a computer-readable storage medium storingcomputer-executable instructions and/or information for performing thefunctions described herein with reference to the systems and/or methodsdisclosed.

FIG. 5 illustrates an example, non-limiting configuration for a PMSMcontrol system 402 that implements one or more features described hereinfor smooth transitioning between reference startup FOC control andclosed-loop sensorless FOC control. In an example embodiment, PMSMcontrol system can be implemented as part of a motor drive (e.g., avariable frequency drive) that controls motion of a PMSM in accordancewith a speed reference signal ω_(Ref) provided by a supervisory motioncontrol application or system. In another example embodiment, PMSMcontrol system 402 may be implemented on one or more processing chips aspart of an embedded system for controlling a PMSM. In yet anotherexample embodiment, PMSM control system 402 can be implemented as partof a motor control module of an industrial controller for control of aPMSM used in an industrial motion control system. It is to beappreciated that the techniques described herein are not limited tothese implementations.

PMSM 504 is a sensorless motor whose motion is controlled by PMSMcontrol system 402. In general, the PMSM control system 402 controls thePMSM using a flux control loop and a torque control loop. Torquereference I_(sqRef) and the flux reference I_(sdRef) represent targetreferences for the torque and flux components, respectively, of thestator currents. As will be described in more detail below, the valuesof I_(sqRef) and I_(sdRef) are controlled differently depending onwhether the PMSM control system 402 is operating in the referencestartup mode or closed-loop sensorless FOC control mode. To providefeedback for the flux and torque control loops, the PMSM control system402 measures the stator currents on two phases of the three-phase ACpower delivered to PMSM 504 and calculates the current for the thirdphase based on the values of the other two phases. Alternatively, thePMSM control system 402 may measure all three phases in order to obtainthe stator currents. A transformation block 418C (implemented bytransformation component 418) transforms the stator current measurementsfrom the three-phase A,B,C reference to the stationary α,β coordinateframework (e.g., a Clarke transformation) to yield I_(s)α and I_(s)β.Transformation block 418B (also implemented by transformation component418) transforms Iα and Iβ to the rotary d,q coordinate framework (e.g.,a Park transformation) to yield I_(sq) and I_(sd). Iq control component414 and Id control component 416 compare the values of I_(sq) and I_(sd)to their corresponding reference values I_(sqRef) and I_(sdRef), andadjust reference voltage values V_(sq) and V_(sd) based on any detectederrors between the measured values I_(sq) and I_(sd) and theircorresponding reference values I_(sqRef) and I_(sdRef).

Transformation block 418A (implemented by transformation component 418)transforms V_(sq) and V_(sd) from the rotary d,q framework to thestationary α,β framework (e.g., an inverse Park transform) to yieldV_(sα) and V_(sβ). Based on these values, a control signal outputcomponent, such as a space vector modulation (SVM) component or pulsewidth modulation (PWM) component 506, controls the AC output of a3-phase inverter 502, thereby controlling motion of the PMSM. Duringclosed-loop sensorless FOC control operation, estimation component 412estimates the angle and speed of the PMSM 504 based on measured statorcurrents I_(sα) and I_(sβ) and reference voltage values V_(sα) andV_(sβ). The estimated velocity ω_(Est) is compared with a speedreference ω_(Ref) (which may be received from a separate supervisorycontrol system or application), and the speed control component 404adjusts I_(sqRef) as needed based on detected errors between the speedreference ω_(Ref) and the estimated velocity ω_(Est).

If the PMSM is starting from a rest position, before initiatingclosed-loop sensorless FOC control, the control system must firstexecute a reference startup FOC control sequence in order to spin themotor at a sufficiently large minimum velocity in order to generatesufficient amount of back-EMF on the motor windings to accuratelyestimate the rotor angle. As described in more detail below, one or moreembodiments of PMSM control system 402 uses the rotor flux projection onthe reference d-axis in order to determine when the applied stator fluxcurrent reference I_(sdRef) is large enough to spin the motor. Thistechnique can mitigate the need to apply an excessively large (e.g.,rated) current during the reference startup phase, thereby reducingenergy consumption relative to systems that use the rated current as thereference current during reference startup operation. Moreover, as willalso be described in more detail below, the system determines an initialstator torque current reference value I_(sqRef) to use at the start ofthe closed-loop sensorless control phase based on the difference betweenthe reference angle θ_(Ref) and the estimated angle θ_(est). Since thisangle difference is reflective of the load on the PMSM, initial torquereference I_(sqRef) determined using the techniques implemented by PMSMcontrol system 402 can facilitate a smooth transition between referencestartup mode and closed-loop sensorless FOC control mode.

An example control sequence is now described with reference to FIGS. 5and 6. FIG. 6 is a set of timing charts illustrating the values of speedreference ω_(Ref); rotor flux projection on reference d-axis λ_(r,sd);stator flux current reference I_(sdRef); and stator torque currentreference I_(sqRef) over time for an example control sequence of a PMSM.This example illustrates a load-adaptive smooth startup method accordingto one or more embodiments of the present disclosure. As noted above,PMSM control system 402 controls reference values I_(sdRef) andI_(sqRef) differently depending on whether the control system 402 isoperating in reference startup control mode or closed-loop sensorlessFOC control mode. This variable control is represented by switchingcomponent 510, which is shown in FIG. 5 as being configured forreference startup operation. That is, for the reference startup phase,I_(sdRef) and I_(sqRef) are controlled by startup current referencecomponent 406, and reference angle θ_(Ref) generated by the startupangle reference component 408 is used by the torque and flux controlloops rather than the estimated angle θ_(est).

At time t=0, the PMSM is at rest. To initiate reference startup FOCcontrol, the startup current reference component 406 gradually increasesthe flux reference I_(sdRef) to a predefined value I_(SD0). Although anysuitable value for I_(SD0) can be used, I_(SD0) will generally besmaller than the rated current; e.g., 20% of the rated current. Fromtime t=0 to t1, reference I_(sdRef) increases from zero to I_(SD0), asshown in timing chart 606.

When I_(sdRef) has reached I_(SD0) at time t=t1, a reference speedsignal ω_(Ref) is received, as shown in timing chart 602. The referencespeed signal is gradually increased to ω_(cmd), e.g., a target speedprescribed by a master control application that provides the referencespeed signal to the PMSM control system 402.

Prior to reaching ω_(cmd), ω_(Ref) will reach a predefined thresholdvalue Ω₁ at time t=t2. Upon reaching the predefined threshold value Ω₁,the startup current reference component 406 determines the rotor fluxprojection on the d-axis λ_(r,sd) based on the following equation:λ_(r,sd)=λ_(sd) −L _(sd) I _(sd)  (1)

where λ_(sd) is the stator flux along the d-axis, L_(sd) is the statorinductance along the d-axis (which can be obtained from the motor datasheet for the PMSM or measured using a self-commissioning method), andI_(sd) is the stator current along the d-axis.

The stator flux λ_(sd) in equation (1) can be obtained based on themeasured back-EMF voltages (e.g., by the estimation component 412) usingany suitable method. In an example, non-limiting technique for obtainingthe stator flux λ_(sd), the measured back-EMF voltages are used todetermine the stator flux in the α, β stationary framework coordinatesystem according to the following equations:λ_(s∝)=∫(V _(s∝) −R _(s) I _(s∝))dt  (2)λ_(sβ)=∫(V _(sβ) −R _(s) I _(sβ))dt  (3)

where λ_(sα) and λ_(sβ) are the stator flux along the α- and β-axes (thestationary framework coordinate system), V_(sα) and V_(sβ) are theapplied stator voltages along the α- and β-axes (generated bytransformation block 418A), I_(sα) and I_(sβ) are the measured statorcurrents along the α- and β-axes (determined by transformation block418C based on the measured stator currents), and R_(s) is the statorresistance (obtained from the motor data sheet or measured using anysuitable self-commissioning method).

The stator flux in the d,q rotary framework coordinate system is thendetermined using the Park transformation of the flux in the stationaryframework:(λ_(sd),λ_(sq))=Park(λ_(s∝),λ_(sβ))  (4)

where λ_(sd) and λ_(sq) are the stator flux along the d- and q-axes (therotary framework coordinate system). The resulting value of λ_(sd) isused in equation (1) to determine the rotor flux projection on thed-axis λ_(r,sd).

Equation (1) is based on the observation that the rotor flux projectionon the reference d-axis is equal to λ_(r) cos(Δθ). FIG. 7 is a graph 700illustrating projection of the rotor flux λ_(r) on the reference q,dcoordinate system. As shown in graph 700, the rotor flux along thed-axis and q-axis is given by λ_(r) cos(Δθ) and λ_(r) sin(Δθ),respectively (where Δθ is the angle difference between the d-axis andthe rotor flux). The stator flux λ_(sd) and λ_(sq) in the rotaryframework is caused by the current run through the inductance and therotor flux, according to the following equations:λ_(sd) =L _(sd) I _(sd) cos(Δθ)λ_(r)  (5)λ_(sq) =L _(sq) I _(sq) sin(Δθ)λ_(r)  (6)

where Δθ is the angle between the d-axis and rotor flux (see FIG. 7);I_(sd) and I_(sq) are the stator current along the d-axis and q-axis,respectively; L_(sd) and L_(sq) are stator inductances along the d-axisand q-axis, respectively, which are obtained from the motor datasheetfor the PMSM or measured using any suitable self-commissioning method;and λ_(r) is the rotor flux magnitude (known or identified). SubtractingL_(sd)I_(sd) from both sides of equation (5) yieldsλ_(sd) −L _(sd) I _(sd)=cos(Δθ)λ_(r)=λ_(r,sd)

Once the startup current reference component 406 determines the rotorflux projection λ_(r,sd) on the d-axis using equation (1), startupcurrent reference component 406 compares the determined value ofλ_(r,sd) with λ_(r) cos(Θ₀), where Θ₀ is a predefined value (e.g., π/3).A low-pass filter is applied to the λ_(r,sd) calculation. The appliedstator flux current reference I_(sdRef) is assumed to be large enough tospin the motor if rotor flux projection λ_(r,sd) is equal to or greaterthan λ_(r) cos(Θ₀).

If it is determined, based on the comparison, that λ_(r,sd) is less thanλ_(r) cos(Θ₀), the startup current reference component 406 increases thestator flux current reference I_(sdRef) until it reaches a predefinedvalue I_(sdmax) (which may be set to the rated current), or until rotorflux projection λ_(r,sd) becomes greater than or equal to λ_(r) cos(Θ₀),causing the rotor to spin. As can be seen on timing chart 604,projection λ_(r,sd) becomes greater than or equal to λ_(r) cos(Θ₀) attime t=t3, when reference I_(sdRef) reaches I_(SD1). At this time, therotor flux projection λ_(r,sd) on the stator d-axis is considered largeenough and reference I_(sdRef) is held constant at I_(SD1) to force therotor to follow the reference speed ω_(Ref).

At this point, the startup current reference component 406 starts todetermine the angle difference Δθ between the reference angle of theI_(sdRef) vector and the estimated angle (estimated based on themeasured stator currents). FIG. 8 is a graph 800 of the projection ofcurrent reference I_(sdRef) on the estimated d,q coordinate system,showing the angle difference Δθ between the I_(sdRef) vector and theestimated rotary coordinate frame. A low-pass filter can be applied toΔθ in order to obtain a smoother signal. As the estimation component 412obtains a more accurate estimation, Δθ will eventually converge to asteady state Θ₁, which reflects the load on the PMSM. Timing chart 604shows the value of Δθ converging to Θ₁ at time t=t4. Since Θ₁ is afunction of the load on the PMSM, this value is used as the basis forthe initial value of reference I_(sqRef) for the closed-loop sensorlessFOC control phase.

Once the value of θ₁ is determined, the startup current referencecomponent 406 sets the initial reference I_(sqRef) as:I _(sqRef) =I _(SD1) sin(Θ₁)  (7)

With the estimation component 412 ready at time t=t4 (as determinedusing any suitable detection method, or based on a determination that apredefined speed has been obtained), the system transitions from controlbased on the reference angle θ_(Ref) to control based on the estimatedangle θ_(Est), as represented by the lower-most switch of switchingcomponent 510. The system can make this transition gradual to facilitatesmooth operation. For example, an angle blending method can be used totransition from the reference angle θ_(Ref) to the estimated angleθ_(Est). At the same time, as shown in timing charts 606 and 608, thestartup current reference component 406 will decrease the referenceI_(sdRef) from I_(SD1) to zero, and will ramp the reference I_(sqRef)from 0 to I_(SD1) sin(Θ₁) between time t=t4 and t=t5. This periodrepresents a transition period between reference startup FOC control andclosed-loop sensorless FOC control.

After time t=t5, the system is in the closed-loop sensorless FOC controlregion, and the PMSM is controlled in accordance with the external speedreference signal ω_(Ref). FIG. 9 depicts the example PMSM control system402 with the switching component 510 configured for closed-loopsensorless FOC control (beginning at time t=t5). Torque referenceI_(sqRef) is now controlled by speed control component 404, whichcontrols the value of I_(sqRef) based on the error between the speedreference ω_(Ref) and the estimated speed ω_(Est) determined byestimation component 412 (based on the measured back-EMF). Fluxreference I_(sdRef) is now controlled by field weakening component 410.In an example scenario, field weakening component 410 may hold referenceI_(sdRef) at zero unless motor operation enters the field weakeningregion. Estimated angle θ_(Est) is used as the feedback angle θ for thepark and inverse park transforms rather than reference angle θ_(Ref).Since the initial value of reference I_(sqRef) when closed-loopsensorless control begins is reflective of the load on the PMSM, thetransition between reference startup FOC control and closed-loopsensorless FOC control will be smooth.

FIG. 10 depicts timing charts 602, 604, 606, and 608 extended in time toillustrate transition from closed-loop sensorless FOC control back toreference startup control according using techniques described herein.At time t=t6, the reference speed ω_(Ref) begins decreasing to return tothe reference startup FOC control state. At time t=t7, the controlsystem begins switching from the estimated angle θ_(Est) to thereference angle θ_(Ref) for control of the PMSM (e.g., using an angleblending technique), where the reference angle is the integration of thereference speed ω_(Ref) with the initial value of the estimated angleθ_(Est) when the transition begins. At the same time, between time t=t7and t=t8 (the transition period between closed-loop sensorless FOCcontrol and reference startup control), the startup current referencecomponent 406 reduces reference I_(sqRef) to 0, and increases referenceI_(sdRef) from 0 to I_(SD1) (the value previously determined at timet=t3 as being the value of I_(sdRef) when λ_(r,sd) became greater thanor equal to λ_(r) cos(Θ₀).

During the reference startup FOC control stage beginning at time t=t8,the rotor flux projection on the stator d-axis is again compared withλ_(r) cos(Θ₀), and I_(sdRef) is adjusted accordingly. If the speedcontinues decreasing to negative speed—reversing the direction ofrotation of the PMSM, beginning at the zero crossover point of timingchart 602—a new angle difference Θ₂ is determined and used for theinitial value of reference I_(sqRef) during transition to closed-loopsensorless FOC control.

Although the example above uses the current reference on the d-axis todetermine the appropriate initial value for reference I_(sqRef), thetechniques described above can also be applied to the reference startupFOC control with the current reference on the q-axis instead of thed-axis, with corresponding modifications to the equations. For example,the quantities in equation (1) determined along the d-axis can bereplaced by their corresponding quantities along the q-axis, and therotor flux projection λ_(r,sq) on the q-axis can be compared with λ_(r)sin(Θ₀)—rather than λ_(r) cos(Θ₀)—in order to determine when there issufficient spin on the motor.

FIGS. 11A-11B illustrate an example methodology in accordance withcertain disclosed aspects. While, for purposes of simplicity ofexplanation, the methodology is shown and described as a series of acts,it is to be understood and appreciated that the disclosed aspects arenot limited by the order of acts, as some acts may occur in differentorders and/or concurrently with other acts from that shown and describedherein. For example, those skilled in the art will understand andappreciate that a methodology can alternatively be represented as aseries of interrelated states or events, such as in a state diagram.Moreover, not all illustrated acts may be required to implement amethodology in accordance with certain disclosed aspects. Additionally,it is to be further appreciated that the methodologies disclosedhereinafter and throughout this disclosure are capable of being storedon an article of manufacture to facilitate transporting and transferringsuch methodologies to computers.

FIG. 11A illustrates a first part of an example methodology 1100A forsmoothly transitioning from reference startup FOC control of a PMSM toclosed-loop sensorless FOC control. Initially, at 1102 with the PMSM atrest, the flux component of a stator control current reference signalI_(sdRef) is increased to a predefined value I_(SD0) that is less thanthe rated current of the PMSM (e.g., 20% of the rated current). At 1104,a reference speed signal ω_(Ref) is increased to at least a predefinedvalue Ω₁.

At 1106, when the reference speed signal has reached Ω₁, the rotor fluxprojection on the d-axis of the rotary framework coordinate systemλ_(r,sd) is determined. The rotor flux projection can be determined, forexample, using equation (1) described above. At 1108, a determination ismade regarding whether the rotary flux projection λ_(r,sd) is greaterthan or equal to λ_(r) cos(Θ₀), wherein Θ₀ is a predefined value (e.g.,π/3). If it is determined at step 1108 that the rotary flux projectionλ_(r,sd) is not greater than or equal to λ_(r) cos(Θ₀) (NO at step1108), the stator d-current reference signal I_(sdRef) is increased at1110, and a determination is made regarding whether I_(sdRef) hasreached a maximum value. If I_(sdRef) has reached its maximum value (YESat 1112), the methodology moves to the second part of the methodology1100B, described below. Alternatively, if I_(sdRef) has not reached itsmaximum (NO at 1112), the methodology returns to step 1106, where therotor flux projection λ_(r,sd) is again determined, and the new fluxprojection λ_(r,sd) is compared with λ_(r) cos(Θ₀) at step 1108. Steps1106-1112 are repeated until either I_(sdRef) reaches its maximum value,or until projection λ_(r,sd) becomes greater than or equal to λ_(r)cos(Θ₀) (YES at step 1108), at which time the methodology proceeds tothe second part 1100B.

FIG. 11B is the second part of the example methodology 1100B. At 1114,the value of I_(sdRef) at or around the time that λ_(r,sd) becamegreater than or equal to λ_(r) cos(Θ₀) (or the time that I_(sdRef)reached its maximum value) is maintained (referred to herein asI_(SD1)). At 1116, the angle difference Δθ between the reference angleof the I_(sdRef) vector and the estimated angle (estimated based on themeasured stator currents). This angle difference, which is a function ofthe unknown load on the PMSM, will converge to a steady value Θ₁.

Steps 1118-1122 may be performed concurrently, or during overlappingtime periods. At 1118, an angle blending technique is used to transitionfrom control using the reference angle to control using the estimatedangle. At 1120, reference I_(sdRef) is reduced from I_(SD0) to zero. At1122, reference I_(sqRef) the torque component the stator controlsignal—is increased from zero to I_(SD1) sin(Θ₁), where I_(SD0) is thevalue of the reference signal I_(sdRef) determined at step 1114, and Θ₁is the angle difference determined at step 1116. Using I_(SD1) sin(Θ₁)as the initial value for reference I_(sqRef) at the start of closed-loopsensorless FOC control can facilitate a smooth transition from thereference startup FOC control mode to the closed-loop sensorless FOCcontrol mode. At 1124 closed-loop sensorless FOC control of the PMSM isperformed using I_(SD1) sin(Θ₁) as the initial value of referenceI_(sqRef).

It is to be appreciated that certain steps of the methodologyillustrated in FIGS. 11A and 11B can be modified to use the rotor fluxprojection λ_(r,sq) on the q-axis rather than λ_(r,sd) on the d-axis.For example, in such an operating scenario, the decision step 1108 willcompare λ_(r,sq) with λ_(r) sin(Θ₀) rather than λ_(r) cos(Θ₀).

Exemplary Networked and Distributed Environments

One of ordinary skill in the art can appreciate that the variousembodiments described herein can be implemented in connection with anycomputer or other client or server device, which can be deployed as partof a computer network or in a distributed computing environment, and canbe connected to any kind of data store where media may be found. In thisregard, the various embodiments of the motion profile generating systemdescribed herein can be implemented in any computer system orenvironment having any number of memory or storage units (e.g., memory422 of FIG. 4), and any number of applications and processes occurringacross any number of storage units. This includes, but is not limitedto, an environment with server computers and client computers deployedin a network environment or a distributed computing environment, havingremote or local storage. For example, with reference to FIG. 4, speedcontrol component 404, startup current reference component 406, startupangle reference component 408, field weakening component 410, estimationcomponent 412, Iq control component 414, Id control component 416, andtransformation component 418 can be stored on a single memory 422associated with a single device, or can be distributed among multiplememories associated with respective multiple devices. Similarly, speedcontrol component 404, startup current reference component 406, startupangle reference component 408, field weakening component 410, estimationcomponent 412, Iq control component 414, Id control component 416, andtransformation component 418 can be executed by a single processor 420,or by multiple distributed processors associated with multiple devices.

Distributed computing provides sharing of computer resources andservices by communicative exchange among computing devices and systems.These resources and services include the exchange of information, cachestorage and disk storage for objects. These resources and services canalso include the sharing of processing power across multiple processingunits for load balancing, expansion of resources, specialization ofprocessing, and the like. Distributed computing takes advantage ofnetwork connectivity, allowing clients to leverage their collectivepower to benefit the entire enterprise. In this regard, a variety ofdevices may have applications, objects or resources that may participatein the various embodiments of this disclosure.

FIG. 12 provides a schematic diagram of an exemplary networked ordistributed computing environment. The distributed computing environmentincludes computing objects 1210, 1212, etc. and computing objects ordevices 1220, 1222, 1224, 1226, 1228, etc., which may include programs,methods, data stores, programmable logic, etc., as represented byapplications 1230, 1232, 1234, 1236, 1238. It can be appreciated thatcomputing objects 1210, 1212, etc. and computing objects or devices1220, 1222, 1224, 1226, 1228, etc. may comprise different devices, suchas personal digital assistants (PDAs), audio/video devices, mobilephones, MP3 players, personal computers, laptops, tablets, etc., whereembodiments of the profile generator described herein may reside on orinteract with such devices.

Each computing object 1210, 1212, etc. and computing objects or devices1220, 1222, 1224, 1226, 1228, etc. can communicate with one or moreother computing objects 1210, 1212, etc. and computing objects ordevices 1220, 1222, 1224, 1226, 1228, etc. by way of the communicationsnetwork 1240, either directly or indirectly. Even though illustrated asa single element in FIG. 12, communications network 1240 may compriseother computing objects and computing devices that provide services tothe system of FIG. 12, and/or may represent multiple interconnectednetworks, which are not shown. Each computing object 1210, 1212, etc. orcomputing objects or devices 1220, 1222, 1224, 1226, 1228, etc. can alsocontain an application, such as applications 1230, 1232, 1234, 1236,1238, that might make use of an API, or other object, software, firmwareand/or hardware, suitable for communication with or implementation ofvarious embodiments of this disclosure.

There are a variety of systems, components, and network configurationsthat support distributed computing environments. For example, computingsystems can be connected together by wired or wireless systems, by localnetworks or widely distributed networks. Currently, many networks arecoupled to the Internet, which provides an infrastructure for widelydistributed computing and encompasses many different networks, thoughany suitable network infrastructure can be used for exemplarycommunications made incident to the systems as described in variousembodiments herein.

Thus, a host of network topologies and network infrastructures, such asclient/server, peer-to-peer, or hybrid architectures, can be utilized.The “client” is a member of a class or group that uses the services ofanother class or group. A client can be a computer process, e.g.,roughly a set of instructions or tasks, that requests a service providedby another program or process. A client process may utilize therequested service without having to “know” all working details about theother program or the service itself.

In a client/server architecture, particularly a networked system, aclient can be a computer that accesses shared network resources providedby another computer, e.g., a server. In the illustration of FIG. 12, asa non-limiting example, computing objects or devices 1220, 1222, 1224,1226, 1228, etc. can be thought of as clients and computing objects1210, 1212, etc. can be thought of as servers where computing objects1210, 1212, etc. provide data services, such as receiving data fromclient computing objects or devices 1220, 1222, 1224, 1226, 1228, etc.,storing of data, processing of data, transmitting data to clientcomputing objects or devices 1220, 1222, 1224, 1226, 1228, etc.,although any computer can be considered a client, a server, or both,depending on the circumstances. Any of these computing devices may beprocessing data, or requesting transaction services or tasks that mayimplicate the techniques for systems as described herein for one or moreembodiments.

A server is typically a remote computer system accessible over a remoteor local network, such as the Internet or wireless networkinfrastructures. The client process may be active in a first computersystem, and the server process may be active in a second computersystem, communicating with one another over a communications medium,thus providing distributed functionality and allowing multiple clientsto take advantage of the information-gathering capabilities of theserver. Any software objects utilized pursuant to the techniquesdescribed herein can be provided standalone, or distributed acrossmultiple computing devices or objects.

In a network environment in which the communications network/bus 1240 isthe Internet, for example, the computing objects 1210, 1212, etc. can beWeb servers, file servers, media servers, etc. with which the clientcomputing objects or devices 1220, 1222, 1224, 1226, 1228, etc.communicate via any of a number of known protocols, such as thehypertext transfer protocol (HTTP). Computing objects 1210, 1212, etc.may also serve as client computing objects or devices 1220, 1222, 1224,1226, 1228, etc., as may be characteristic of a distributed computingenvironment.

Exemplary Computing Device

As mentioned, advantageously, the techniques described herein can beapplied to any suitable device. It is to be understood, therefore, thathandheld, portable and other computing devices and computing objects ofall kinds are contemplated for use in connection with the variousembodiments. Accordingly, the below computer described below in FIG. 13is but one example of a computing device. Additionally, a suitableserver can include one or more aspects of the below computer, such as amedia server or other media management server components.

Although not required, embodiments can partly be implemented via anoperating system, for use by a developer of services for a device orobject, and/or included within application software that operates toperform one or more functional aspects of the various embodimentsdescribed herein. Software may be described in the general context ofcomputer executable instructions, such as program modules, beingexecuted by one or more computers, such as client workstations, serversor other devices. Those skilled in the art will appreciate that computersystems have a variety of configurations and protocols that can be usedto communicate data, and thus, no particular configuration or protocolis to be considered limiting.

FIG. 13 thus illustrates an example of a suitable computing systemenvironment 1300 in which one or aspects of the embodiments describedherein can be implemented, although as made clear above, the computingsystem environment 1300 is only one example of a suitable computingenvironment and is not intended to suggest any limitation as to scope ofuse or functionality. Neither is the computing system environment 1300be interpreted as having any dependency or requirement relating to anyone or combination of components illustrated in the exemplary computingsystem environment 1300.

With reference to FIG. 13 an exemplary computing device for implementingone or more embodiments in the form of a computer 1310 is depicted.Components of computer 1310 may include, but are not limited to, aprocessing unit 1320, a system memory 1330, and a system bus 1322 thatcouples various system components including the system memory to theprocessing unit 1320. Processing unit 1320 may, for example, performfunctions associated with processor(s) 420 of PMSM control system 402,while system memory 1330 may perform functions associated with memory422.

Computer 1310 typically includes a variety of computer readable mediaand can be any available media that can be accessed by computer 1310.The system memory 1330 may include computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) and/orrandom access memory (RAM). By way of example, and not limitation,system memory 1330 may also include an operating system, applicationprograms, other program modules, and program data.

A user can enter commands and information into the computer 1310 throughinput devices 1340, non-limiting examples of which can include akeyboard, keypad, a pointing device, a mouse, stylus, touchpad,touchscreen, trackball, motion detector, camera, microphone, joystick,game pad, scanner, or any other device that allows the user to interactwith computer 1310. A monitor or other type of display device is alsoconnected to the system bus 1322 via an interface, such as outputinterface 1350. In addition to a monitor, computers can also includeother peripheral output devices such as speakers and a printer, whichmay be connected through output interface 1350. In one or moreembodiments, input devices 1340 can provide user input to PMSM controlsystem 402, while output interface 1350 can receive and displayinformation relating to operations of PMSM control system 402.

The computer 1310 may operate in a networked or distributed environmentusing logical connections to one or more other remote computers, such asremote computer 1370. The remote computer 1370 may be a personalcomputer, a server, a router, a network PC, a peer device or othercommon network node, or any other remote media consumption ortransmission device, and may include any or all of the elementsdescribed above relative to the computer 1310. The logical connectionsdepicted in FIG. 13 include a network 1372, such local area network(LAN) or a wide area network (WAN), but may also include othernetworks/buses e.g., cellular networks.

As mentioned above, while exemplary embodiments have been described inconnection with various computing devices and network architectures, theunderlying concepts may be applied to any network system and anycomputing device or system in which it is desirable to publish orconsume media in a flexible way.

Also, there are multiple ways to implement the same or similarfunctionality, e.g., an appropriate API, tool kit, driver code,operating system, control, standalone or downloadable software object,etc. which enables applications and services to take advantage of thetechniques described herein. Thus, embodiments herein are contemplatedfrom the standpoint of an API (or other software object), as well asfrom a software or hardware object that implements one or more aspectsdescribed herein. Thus, various embodiments described herein can haveaspects that are wholly in hardware, partly in hardware and partly insoftware, as well as in software.

The word “exemplary” is used herein to mean serving as an example,instance, or illustration. For the avoidance of doubt, the aspectsdisclosed herein are not limited by such examples. In addition, anyaspect or design described herein as “exemplary” is not necessarily tobe construed as preferred or advantageous over other aspects or designs,nor is it meant to preclude equivalent exemplary structures andtechniques known to those of ordinary skill in the art. Furthermore, tothe extent that the terms “includes,” “has,” “contains,” and othersimilar words are used in either the detailed description or the claims,for the avoidance of doubt, such terms are intended to be inclusive in amanner similar to the term “comprising” as an open transition wordwithout precluding any additional or other elements.

Computing devices typically include a variety of media, which caninclude computer-readable storage media (e.g., memory 422) and/orcommunications media, in which these two terms are used hereindifferently from one another as follows. Computer-readable storage mediacan be any available storage media that can be accessed by the computer,is typically of a non-transitory nature, and can include both volatileand nonvolatile media, removable and non-removable media. By way ofexample, and not limitation, computer-readable storage media can beimplemented in connection with any method or technology for storage ofinformation such as computer-readable instructions, program modules,structured data, or unstructured data. Computer-readable storage mediacan include, but are not limited to, RAM, ROM, EEPROM, flash memory orother memory technology, CD-ROM, digital versatile disk (DVD) or otheroptical disk storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or other tangible and/ornon-transitory media which can be used to store desired information.Computer-readable storage media can be accessed by one or more local orremote computing devices, e.g., via access requests, queries or otherdata retrieval protocols, for a variety of operations with respect tothe information stored by the medium.

On the other hand, communications media typically embodycomputer-readable instructions, data structures, program modules orother structured or unstructured data in a data signal such as amodulated data signal, e.g., a carrier wave or other transportmechanism, and includes any information delivery or transport media. Theterm “modulated data signal” or signals refers to a signal that has oneor more of its characteristics set or changed in such a manner as toencode information in one or more signals. By way of example, and notlimitation, communication media include wired media, such as a wirednetwork or direct-wired connection, and wireless media such as acoustic,RF, infrared and other wireless media.

As mentioned, the various techniques described herein may be implementedin connection with hardware or software or, where appropriate, with acombination of both. As used herein, the terms “component,” “system” andthe like are likewise intended to refer to a computer-related entity,either hardware, a combination of hardware and software, software, orsoftware in execution. For example, a component may be, but is notlimited to being, a process running on a processor, a processor, anobject, an executable, a thread of execution, a program, and/or acomputer. By way of illustration, both an application running oncomputer and the computer can be a component. One or more components mayreside within a process and/or thread of execution and a component maybe localized on one computer and/or distributed between two or morecomputers. Further, a “device” can come in the form of speciallydesigned hardware; generalized hardware made specialized by theexecution of software thereon that enables the hardware to performspecific function (e.g., coding and/or decoding); software stored on acomputer readable medium; or a combination thereof.

The aforementioned systems have been described with respect tointeraction between several components. It can be appreciated that suchsystems and components can include those components or specifiedsub-components, some of the specified components or sub-components,and/or additional components, and according to various permutations andcombinations of the foregoing. Sub-components can also be implemented ascomponents communicatively coupled to other components rather thanincluded within parent components (hierarchical). Additionally, it is tobe noted that one or more components may be combined into a singlecomponent providing aggregate functionality or divided into severalseparate sub-components, and that any one or more middle layers, such asa management layer, may be provided to communicatively couple to suchsub-components in order to provide integrated functionality. Anycomponents described herein may also interact with one or more othercomponents not specifically described herein but generally known bythose of skill in the art.

In order to provide for or aid in inferences described herein,components described herein can examine the entirety or a subset of thedata to which it is granted access and can provide for reasoning aboutor infer states of the system, environment, etc. from a set ofobservations as captured via events and/or data. Inference can beemployed to identify a specific context or action, or can generate aprobability distribution over states, for example. The inference can beprobabilistic—that is, the computation of a probability distributionover states of interest based on a consideration of data and events.Inference can also refer to techniques employed for composinghigher-level events from a set of events and/or data.

Such inference can result in the construction of new events or actionsfrom a set of observed events and/or stored event data, whether or notthe events are correlated in close temporal proximity, and whether theevents and data come from one or several event and data sources. Variousclassification (explicitly and/or implicitly trained) schemes and/orsystems (e.g., support vector machines, neural networks, expert systems,Bayesian belief networks, fuzzy logic, data fusion engines, etc.) can beemployed in connection with performing automatic and/or inferred actionin connection with the claimed subject matter.

A classifier can map an input attribute vector, x=(x1, x2, x3, x4, xn),to a confidence that the input belongs to a class, as byf(x)=confidence(class). Such classification can employ a probabilisticand/or statistical-based analysis (e.g., factoring into the analysisutilities and costs) to prognose or infer an action that a user desiresto be automatically performed. A support vector machine (SVM) is anexample of a classifier that can be employed. The SVM operates byfinding a hyper-surface in the space of possible inputs, where thehyper-surface attempts to split the triggering criteria from thenon-triggering events. Intuitively, this makes the classificationcorrect for testing data that is near, but not identical to trainingdata. Other directed and undirected model classification approachesinclude, e.g., naïve Bayes, Bayesian networks, decision trees, neuralnetworks, fuzzy logic models, and probabilistic classification modelsproviding different patterns of independence can be employed.Classification as used herein also is inclusive of statisticalregression that is utilized to develop models of priority.

In view of the exemplary systems described above, methodologies that maybe implemented in accordance with the described subject matter will bebetter appreciated with reference to the flowcharts of the variousfigures (e.g., FIGS. 10A-10B). While for purposes of simplicity ofexplanation, the methodologies are shown and described as a series ofblocks, it is to be understood and appreciated that the claimed subjectmatter is not limited by the order of the blocks, as some blocks mayoccur in different orders and/or concurrently with other blocks fromwhat is depicted and described herein. Where non-sequential, orbranched, flow is illustrated via flowchart, it can be appreciated thatvarious other branches, flow paths, and orders of the blocks, may beimplemented which achieve the same or a similar result. Moreover, notall illustrated blocks may be required to implement the methodologiesdescribed hereinafter.

In addition to the various embodiments described herein, it is to beunderstood that other similar embodiments can be used or modificationsand additions can be made to the described embodiment(s) for performingthe same or equivalent function of the corresponding embodiment(s)without deviating there from. Still further, multiple processing chipsor multiple devices can share the performance of one or more functionsdescribed herein, and similarly, storage can be effected across aplurality of devices. Accordingly, the invention is not to be limited toany single embodiment, but rather can be construed in breadth, spiritand scope in accordance with the appended claims.

What is claimed is:
 1. A system for performing field oriented control ofa permanent magnet synchronous motor (PMSM), comprising: a memory; aprocessor configured to execute computer-executable components stored onthe memory, the computer-executable components comprising: a startupcurrent reference component configured to control a stator flux currentreference and a stator torque current reference of a stator controlsignal during a reference startup mode, wherein the startup currentreference component is configured to set a value of at least one of thestator flux current reference or the stator torque current reference forthe reference startup mode based on a rotor flux projection; a speedcontrol component configured to control the stator torque currentreference during a closed-loop sensorless control mode; a flux weakeningcomponent configured to control the stator flux current reference duringthe closed-loop sensorless control mode; and a control signal outputcomponent configured to output the stator control signal based on thestator flux current reference and the stator torque current reference;wherein the startup current reference component is further configured todetermine the rotor flux projection on the reference d-axis according toλ_(r,sd)=λ_(sd) −L _(sd) I _(sd) where λ_(r,sd) is the rotor fluxprojection on a reference d-axis of a rotary framework coordinatesystem, λ_(sd) is a stator flux along the d-axis, L_(sd) is a statorinductance along the d-axis, and I_(sd) is a stator current along thed-axis.
 2. The system of claim 1, wherein the startup current referencecomponent is further configured to increase the stator flux currentreference during the reference startup mode, and to set a stator fluxcurrent reference value for the reference startup mode equal to a valueI_(SD1) at a time that the rotor flux projection is determined to beequal to or greater than cos(Θ₀)λ_(r), where Θ₀ is a predefined valueand λ_(r) is a rotor flux.
 3. The system of claim 2, wherein the startupcurrent reference component is further configured to, during thereference startup mode, determine an angle difference Θ₁ between areference angle of a vector of the stator flux current reference and anestimated angle determined based on measured stator currents, and to setan initial value of the stator torque current reference for theclosed-loop sensorless control mode based on the angle difference Θ₁. 4.The system of claim 3, wherein the startup current reference componentis further configured to set the initial value of the stator torquecurrent reference for the closed-loop sensorless control mode equal toI_(SD1) sin(Θ₁).
 5. The system of claim 3, wherein the startup currentreference component is further configured to, during an intermediateperiod between the reference startup mode and the closed-loop sensorlesscontrol mode, reduce the stator flux current reference from I_(SD1) tozero, and increase the stator torque current reference from zero toI_(SD1) sin(Θ₁), where I_(SD1) sin(Θ₁) is the initial value of thestator torque current reference for the closed-loop sensorless controlmode.
 6. The system of claim 5, wherein the startup current referencecomponent is further configured to, during the intermediate period,transition from control based on the reference angle to control based onthe estimated angle using an angle blending algorithm.
 7. The system ofclaim 1, further comprising an estimation component configured todetermine estimated values for a position and a velocity of a permanentmagnet synchronous motor (PMSM) based on back-electromagnetic force(back-EMF) values measured from windings of the PMSM.
 8. The system ofclaim 7, wherein the startup current reference component is furtherconfigured to determine a stator flux λ_(s∝) along an α-axis of astationary framework coordinate system and a stator flux λ_(sβ) along aβ-axis of the stationary framework coordinate system according to:λ_(s∝)=∫(V _(s∝) −R _(s) I _(s∝))dtλ_(sβ)=∫(V _(sβ) −R _(s) I _(sβ))dt where V_(sα) and V_(sβ) are appliedstator voltages along the α-axis and the β-axis, respectively, I_(sα)and I_(sβ) are measured stator currents along the α-axis and the β-axis,respectively, and R_(s) is a stator resistance.
 9. The system of claim7, wherein the startup current reference component is configured todetermine the stator flux λ_(sd) by performing a Park transformation onλ_(s∝) and λ_(sβ).
 10. A method for performing sensorless field orientedcontrol of a permanent magnet synchronous motor (PMSM), comprising:determining, by a system comprising at least one processor, a rotor fluxprojection based on a back-electromagnetic force (back-EMF) measuredfrom stator windings; setting, by the system, a value I_(SD1) of astator flux current reference for a reference startup mode based on therotor flux projection; determining, by the system, an initial value of astator torque current reference of the stator control signal based onthe value I_(SD1); and transitioning, by the system, from the referencestartup mode to a closed-loop sensorless control mode using the initialvalue of the stator torque current reference as a starting value;wherein the determining the rotor flux projection comprises determiningthe rotor flux projection based onλ_(r,sd)=λ_(sd) −L _(sd) I _(sd) where λ_(r,sd) is the rotor fluxprojection on a d-axis of a rotary framework coordinate system, λ_(sd)is a stator flux along the d-axis, L_(sd) is a stator inductance alongthe d-axis, and I_(sd) is a stator current along the d-axis.
 11. Themethod of claim 10, wherein the setting the value I_(SD1) of the statorflux current reference comprises: increasing the stator flux currentreference during the reference startup mode; and setting the valueI_(SD1) of the stator flux current reference equal to a value of thestator flux current reference at a time that the rotor flux projectionis determined to be equal to or greater than cos(Θ₀)λ_(r), where Θ₀ is apredefined value and λ_(r) is a rotor flux.
 12. The method of claim 11,wherein the determining the initial value of the stator torque currentreference comprises: determining, during the reference startup mode, anangle difference Θ₁ between a reference angle of a vector of the statorflux current reference and an estimated angle determined based onmeasured stator currents; and setting, the initial value of the statortorque current reference based on the angle difference Θ₁.
 13. Themethod of claim 12, wherein the setting the initial value of the statortorque current reference comprises setting the initial value equal toI_(SD1) sin(Θ₁).
 14. The method of claim 12, wherein the transitioningfrom the reference startup mode to the closed-loop sensorless controlmode comprises: reducing, during an intermediate period between thereference startup mode and the closed-loop sensorless control mode, thestator flux current reference from I_(SD1) to zero; and increasing,during the intermediate period, the stator torque current reference fromzero to I_(SD1) sin(Θ₁), where I_(SD1) sin(Θ₁) is the initial value ofthe stator torque current reference for the closed-loop sensorlesscontrol mode.
 15. The method of claim 14, wherein the transitioning fromthe reference startup mode to the closed-loop sensorless control modefurther comprises transition, during the intermediate period, fromcontrol based on the reference angle to control based on the estimatedangle using an angle blending algorithm.
 16. The method of claim 14,further comprising transitioning, by the system, from the closed-loopsensorless control mode to the reference startup mode, comprising:increasing, during a subsequent intermediate period between theclosed-loop sensorless control mode and the reference startup mode, thestator flux current reference from zero to I_(SD1); and decreasing,during the subsequent intermediate period, the stator torque currentreference to zero.
 17. A non-transitory computer-readable medium havingstored thereon computer-executable instructions that, in response toexecution, cause a computer system to perform operations, comprising:determining a rotor flux projection based on a back-electromageneticforce (back-EMF) measured from stator windings; setting a value I_(SD1)of a stator flux current reference of a stator control signal for areference startup mode based on the rotor flux projection; determiningan initial value of a stator torque current reference based on the valueI_(SD1); and transitioning from the reference startup mode to aclosed-loop sensorless control mode using the initial value of thestator torque current reference as a starting value; wherein thedetermining the rotor flux projection comprises determining the rotorflux projection based onλ_(r,sd)=λ_(sd) −L _(sd) I _(sd) where λ_(r,sd) is the rotor fluxprojection on a d-axis of a rotary framework coordinate system, λ_(sd)is a stator flux along the d-axis, L_(sd) is a stator inductance alongthe d-axis, and I_(sd) is a stator current along the d-axis.